B67 rewind not working

[rotoman]

I checked pin1 on IC2 .5v, I also checked pin7 on IC2 for the supply reel, and got 0v. I pulled Q15 out, you said Q16, but I think you meant Q15.
I checked Q15 with an ohm meter and got 19meg from emitter to base(-)to(+)
Emitter to base(+)to(-)I got infinity. Emitter to collect infinity both ways.

[Michael Maurice]

Pin 7 is the take up reel output, press FF and see what pin 7 reads. Cant determine Q15 from those readings, its probably OK.

[rotoman]

I believe pin 7 is the supply reel according to my manual. Also you said if I get more than 0v on pin 1 Q16 could be bad, which I think you meant Q15??
Maybe we have different manuals, I am confused Sorry, I pulled Q15 out because you said if I get greater than 0v on pin 1 the transistor could be open.
I went ahead and order one, will let you know the out come.

Thanks

[Michael Maurice]

The trouble when you get older is that ones eyesight plays up! I'll scan a copy of my manual so you can see that I mean. i take it your machine isa Mk2

[rotoman]

I know what you mean! I have one of those magnifying lights, without that It would also be very hard for me to read. The tape transport part# on the schematic is 1.167.759
Hope that helps.

[rotoman]

I replaced Q15, no luck. Could the problem be in one of the sensor boards?

[Michael Maurice]

Very unlikely as in Rew/FF the sensor boards control the opposite motor.

so that in Rew for example, full power is given to the LH supply motor and the LH sensor controls the RH,Take up motor so as to maintain the required back tension.

[rotoman]

Michael

Should I start from output of the transport board, and compare dc voltages (RH, & LH)to see if there are differences when I press rewind/Fast Forward. I can load it with tape, I have the transport board out of the deck so I can check voltages. If you can tell me what points to check, and what voltages I should see that would be great.

Thanks, Tony

[Michael Maurice]

Yes the fault is on the transport board.

[rotoman]

Ok I guess I am on my own, Thanks for all your help.

[Michael Maurice]

I will try and help you but I dont have a Studer B67,the nearest I have is a Revox A700 which uses the dreaded TCA560 IC's.

I'll see if I can ask a couple of other members for their input.

You really need to put the machine into permanent rewind without a tape so you can take measurements.

The other thing you can do is look out for a tape transport card, they do come up from time to time.

[Michael Maurice]

I've had a good look at the diagram for the tape transport board.

For what its worth I think your fault is somewhere between IC4 and Q15 because this is common in all modes.

Lets get a few things straight.

The Supply motor, ie LH motor is M1 which comes from the tape transport board from YAN M1, this in turn is supplied from Q15 not Q16!

If you follow the diagram, I've marked the path in red, it goes to a sub PCB with 6 presets on them, which is marked Supply Motor and Take Up Motor.

The presets are: PLAY, PEAK, FORW, PEAK REW PLAY.

In Rew follow the line back through the PEAK preset it goes back to the lamp associated with rewind and the transistor Q7.

When REW is selected, the collector of Q7 goes low, ie to near 0V, the lamp B5 lights and if this lamp has failed, resistor R50 provides a load to Q7's collector.

The collector of Q7 is connected to the SUPPLY MOTOR PEAK preset which goes to IC4's inverting input.

The rest is reasonably straightforward to follow

Though I cant explain what IC5 is for!

IC2 introduces a small amount of 100HZ pulses not DC.

I suggest you put the machine into rewind and carry out checks around IC4, IC1, IC5 and IC2.

I believe that the IC's are pluggable, on these boards. if this is the case, you could swop IC5 and IC6 to eliminate it. You should also check the high value resistors to see if one of them has gone OC.

Please look at the diagrams I've posted.

[Ted Kendall]

First thought was the motor phase shift condensor, but the motor runs under test, so that's out. It isn't unknown for one of the pots on the torque adjustment PCB to go sour, and this can cause this kind of behaviour in the A810, which has similar topology in this area. It's as if the control is asking for an impossibly low tension, so the motor is backed right off even if the tension arm is on the end stop.

[rotoman]

Wow! Thanks everyone for the advise, I am sick with the flu so things are on hold , I will get back to everyone next week.

[rotoman]

Hi Michael

The deck is still on the work bench collecting dust, but I haven't given up just a lot of things happening in my life. The IC's are soldered to the board so I will order some IC sockets. I purchased some of the IC's but some are discontinued.

Tony

[rotoman]

Hi

I have found a replacement tape transport card for my deck, it is for a B67 MRK I which is what I have, but the part numbers are different.
I have part# 1.167.759-11 installed on my deck now, The replacement card
is part# 1.167.761-11 with a 1 inside a circle after the part#.
The schematics of both of these cards have the identical female connector arangement/supply voltages, but it has some different IC's/circuit arrangements. It appears to be a revision to the prevous card.
Can someone tell me if this replacement card will work on my deck

Thanks, Tony

[rotoman]

Hi

I replaced my transport card with a known functional card, and the probblem still exist with only play, and FF functions, no rewind function. What other areas can I check that may cause this problem?? If you read the history of this post you can see what test that was preformed to lead us to this point.

Thanks for all your help to date.

Tony

[rotoman]

gotta be someone out there with an idea?

[Michael Maurice]

Yes there probably is, but please dont forget that we are not always glued to our computers!
Having said that

In post #19 you said that you measured the voltage on the base of the transistor and got 0V.

Now carry out the same test again but measure on the connector of the transport board.

What may be the problem is that the wire itself is broken, possibly at the crimp of the spade connector.

[rotoman]

Michael sorry

Ok here is the the test I done today, I loaded the machine with tape so I wouldn't have to do the jumper thing.
I took my probe negative on yellow wire of spooling motor control board (0-M1)
which I assume is ground, it is the same potential as pin 1 on J1 of transport board. I took my positive lead, and checked YB1-MOVE pin 5 on J1(transport) I got .08V then I checked Y1-END pin 6 on J1(transport) I got 4.72V.
Then I put the Machine in RR I got YB1-move 4.13V, Y1-END 4.70V, please note that reels turn in FF mode in FF,and RR modes. I put the machine in RR again, and checked pin 12 of J4(YAN-M1) I got .121V please not I also have .121V when machine is idle. I also checked these voltages for YAN-M1 at the transport board, and spooling motor board to rule out bad connection.
Hope this info helps

Again Michael thanks for your help, this machine has been down for a while, I am not in any way in a hurry, when ever you get time thats fine with me.

Tony